Hello scientists, my name is Mr. Wilshire, and in this lesson we're going to be looking at reflected light.

This is the plan stage.

The outcome for this lesson is, I can plan how to compare different materials based on how reflective they are.

There are a few keywords to consider as we work our way through this lesson.

The first is reflect.

Then reflective.

After that, surface.

Then it's data logger.

And finally, lux.

I wonder if you've heard any of these words before.

Don't worry if you're not too sure what all of them mean as the definitions have been put on the screen for you now.

We're also going to be using them throughout this lesson.

If you need to, you can remind yourself by pausing the video and continuing when you're ready.

The first part of this lesson is called reflected light.

Alex and his brother are on a nighttime walk with their dad.

As a car passes and shines its headlight, Alex notices parts of his brother's coat appear to light up too.

Here's Alex's brother, and there's Alex, and there's Alex's brother's coat.

Oh, yes, I can see that there are two little strips on there that are lighting up.

Why do you think this happens, though? The whole coat isn't shining, is it? Why is it that these parts are shining in this way? Pause the video and discuss.

Restart when you've done that.

How'd you get on? I wonder why parts of Alex's brother's coat are lighting up.

Well, Alex's brother explains that the coat isn't a light source.

The material of the coat is reflecting light.

Ah, right, so the coat isn't shining things out, no, but it's actually reflecting the light back from the cars that are going by.

Alex says, "Well, I've heard about reflections when I look in the mirror, but the coat isn't a mirror." Here you can see an image of an apple reflected in a mirror.

This is right, the coat's not a mirror.

If you were to look into the back of a coat, you're not gonna be able to see yourself, are you? So what does that mean? How is it reflective? Alex's brother again explains that reflection involves a source of light and a surface.

He continues, "When light reaches a surface which it can't pass through, it can sometimes bounce or reflect off of that surface." There you can see the light from the torch, it's shining onto the surface, and then the light reflected from the surface bounces back again.

Doesn't necessarily mean that it's going to be bouncing back in this exact way.

That beam of light is gonna be shining from one of the source to the surface and then back out again.

So in this case, Alex's eyes are able to pick up that the light is bouncing off the surface and back towards him.

Now, Alex's brother's coat is made of a reflective material, so when light hits the surface of the coat, it bounces off.

This is called reflected light.

You can see the car headlights shining out, and you can see the light is reflected by the surface of the coat, and then up to Alex as well.

Doesn't mean that only Alex would be able to see this, it would mean that the car driver would also be able to see this, and anyone else walking past as well.

The reflected light is spread out so everybody can see.

Let's stop and think, is this is true or false? Reflection always involves a source of light and a mirror.

The correct answer here is false.

Can we justify our answer here? Is it because reflection involves a source of light and a reflective surface? Or is it because reflection involves a source of light and a shadow? The correct answer is A, reflection involves a source of light and a reflective surface.

The children stand under the nearest street light to observe if surfaces reflect light.

Here you can see a street light shining into the night sky.

I wonder if you've ever observed any materials that reflect light as well.

Have you noticed this before? Discuss.

You may have seen this before when you were walking along, especially in the winter when it's darker earlier on in the day and you need to wear a coat.

You may have even spotted that your coat has got some reflective surfaces on them as well, or maybe some special patches.

Maybe you've even seen these type of reflective things on other items as well that you use.

As the children are walking home, Alex realises that he's lost his hat.

He and his brother can't find it in the dark, even when they use their torches.

So Alex's hat is lost.

And it's nice and bright and red.

So even searching with the torches, they still can't see it very well.

Oh, his brother and Alex finally find the missing hat, and his brother has an idea.

He says, "Well, you could use a piece of reflective material.

You could put that on your hat to reflect the light from our torches, and then you will easily be able to find it if you lose it again." Hmm, that's a pretty good idea.

You could put the reflective material on there and then when you shine a light on it, then you're gonna be able to find it.

Also, it's gonna make it nice and safe if you're out walking in the dark in the winter.

You can keep warm and you can be seen.

Alex says, "I found some different materials.

We could test them to find out how reflective they are." Here are the materials that Alex has got.

He's got white card, black card.

I'm glad he's got some card and not just paper because the paper might be a little bit flimsy.

He's got some foil, some baking paper, a plastic bag, some cotton fabric, a mirror, and some laminated paper.

Hmm, I wonder if you've ever used any of these materials before and if you know if they're reflective already? You may be going into this investigation with some extra knowledge already.

So how can Alex find out which materials are most suitable for reflecting light? Have a discussion and restart the video when you've done that.

How did you get on? How can Alex find out which materials are most suitable for reflecting light, then? What's the best thing to do? Well, Alex says, "I'm going to go into a dark room.

I'm gonna shine my torch on different materials and observe whether they reflect any light back onto the wall.

These will be suitable reflective materials for my hat." So he's got his torch there, he's got his surface of material and the wall.

So he's gonna see by looking to the side, not at the material.

He needs to work out if the material is definitely reflecting the torch light onto the wall.

So there's the light from Alex's torch, the light reflected by the surface.

And Alex is gonna have to look there, isn't he? So Alex begins by testing a mirror.

He holds a mirror so that it's facing the wall.

There's the mirror, there's the torch.

He shines it towards the mirror and he looks at the wall to observe if any light has been reflected off the mirror onto the wall.

And he writes down what he observes.

What can you see here? What can you observe? Have a think while we move on to the next question.

Which diagram shows how light reflects from a surface onto a wall? Is it A or is it B? The correct answer here is B.

Of course, yes, you can see the arrows there clearly showing the direction that the light is taking.

So here is task A.

Use Alex's method to test different materials to find out which materials are most suitable for reflecting light.

You've got some items there, or you may choose to use some slightly different materials if you wish.

There's a light source, which could be a torch, or you may be using something else.

You've got the surface of material to bounce the light, reflecting it onto the wall.

Remember to dim the lights.

And if it is rather dark where you are working, don't forget to be very careful.

Best of luck with your task.

Restart the video when you've done that.

How did you get on? Your results might be similar to this.

Remember, if you use some different materials, it could come out slightly different.

Alex says, "I observed that the mirror and the foil reflected light from the torch onto the wall, but it was difficult to tell if any other materials I tested were suitable reflective materials." I wonder why it was so difficult.

Did you find this out as well? The last part of this lesson is called measuring reflected light.

Well, Alex observed that light was reflected onto the wall using a mirror and some kitchen foil.

There you can see clearly that the torch is definitely being reflected off of the mirror.

Alex says, "Are mirrors and kitchen foil the only reflective materials, though? I thought other materials would reflect some light as well." His brother then says, "Well, nearly all materials reflect some light.

Mirrors, however, reflect almost all the light that hits them due to their nice shiny surface." Alex says, "Well, I'd like to find out how much light is reflected from the surface of different materials.

I wonder if I can actually measure reflected light." What do you think? Is Alex going to be able to measure reflected light? Is there a special tool that he needs, or maybe some sort of special device? Have a discussion and a think.

Restart when you've done that.

How did you get on? Is there something that you've heard of before that can measure light? Let's find out more.

Alex says, "Well, I need to find something that can measure how much light is reflected from the surface of each material.

I know that a thermometer can measure temperature and a stopwatch can measure time, but what can I use to measure light?" Very good question.

What do you think? How is he going to measure light? Andeep comes along to explain.

He says, "We can use a data logger.

It's got a light sensor to monitor and record how much light each material reflects." The data logger that they're using looks a little bit like this.

Have you ever used a data logger before? Tell someone nearby about your experience of using a data logger, or maybe something similar to this.

Hopefully you've had a good chance to discuss how you've used a data logger before.

If you haven't, don't worry, because there are lots of different ways that you can have a go at measuring light without a data logger as well.

If you haven't, don't worry, because I'm sure at some point in your time at school you'll be able to use a device a little bit like this that will measure different items. Now, light data can be recorded on a data logger.

The data logger that you've used before may look something similar to this.

Data loggers are incredible machines because they can measure temperature, they can measure sound, in this case, they're measuring light.

But there are also different apps that you might be able to download onto a device.

This can then help your device to use some of the tools that it already has, like a camera or even a microphone to be able to measure different elements.

In this case, we're measuring light using a data logger.

Data loggers do also come in all sorts of different shapes and sizes, so don't worry if yours that you're using looks a little different to this one.

So Alex's idea here is to dim the lights.

He's going to dim the lights in the room.

And he then says, "I'm gonna shine my torch towards each material and the data logger will display a number.

The higher the number, the more light is being reflected.

Light is measured in lux." Can you see that on the screen there? It says 65 lx.

So lx is a short way of measuring lux, a little bit like when you are writing the measurement for something in centimetres, you wouldn't write centimetres all the time, you would write cm.

In this way, you can see that lux can be written as lx.

Stop and think, which of these do we use to measure and record light, a clock, a data logger, or a tape measure? The correct answer here is a data logger.

It's B.

Andeep and Alex use a ruler to keep the position of the data logger and torch the same distance from the material each time.

There you can see the torch 20 centimetres from the material, you can see the ruler, you can see the data logger.

It's 10 centimetres away.

And you can see the material.

Excellent, they've set this experiment up really nicely.

So they're going to be able to move the different materials around then, and then that's going to reflect the light towards the data logger, which can then pick up the reading.

Who do you agree with here? Aisha says, "Light can be measured with weighing scales and is measured in kilogrammes." Sam says, "Light can be measured with a data logger and is measured in lux." Lucas says, "Light can be measured with a measuring jug and is measured in millilitres." Who's got it right? Well, the person I agree with here is Sam.

Light can be measured with a data logger and is measured in lux.

Here is task B.

Plan your own test now to find out how much light is reflected from the surface of different materials.

You need to write down what you'll need to do and what you will do.

Remember to think about what you will change and what you will keep the same as well.

You could use Alex and Andeep's idea, or you might prefer to plan your own investigation.

So some of the materials could be very similar to the ones that we've suggested, or you might have some of your own ideas.

Or you could trial the ones that we've suggested and even add some of your own ideas in as well.

Don't forget to record all this information down as well.

You might need to think of a good way to do that.

Best of luck with your task.

Restart the video when you've done that.

How did you get on? Well, here is an example of some things that could be needed.

Yours could be similar to this.

So what the children decided to need was a ruler, a data logger and a torch.

The materials, white card, black card, foil, baking paper, plastic bag, cotton fabric, a mirror, and laminated paper.

What they're going to do, they're going to make the room as dark as possible.

They're going place the light source 20 centimetres away from the material.

They're going to place the data logger facing the material at a distance of 10 centimetres away.

They're going to record the measurement in lux, recorded on the data logger.

Then they're going to repeat with each type of material.

Don't forget, instead of using a data logger, you could use an app downloaded onto a similar device.

Well, hopefully your planned investigation is similar to this.

And maybe it's got some slight tweaks and changes or things that we may have forgotten about here.

I wonder what other materials you've chosen to use to reflect light as well.

Let's summarise our lesson.

Reflection involves a source of light and a surface.

Light reflected from a surface is called reflected light.

Data loggers are electronic devices which monitor and record changes in the environment over time.

Light is measured in lux, also known as lx.

It can be recorded using a data logger.

And there's Alex there with his lovely red hat with a big reflective strip on it.

Maybe you've got a better idea about the different ways that we can record light.

I wonder why this would be useful in the day-to-day world, measuring light.

Maybe if you wanted to create the perfect type of light that you could use in a TV studio, you would need to know how powerful it can be.

And if there are any other services in that studio which might reflect the light too much.

So you're going to need to investigate to find the best type of materials to use to make sure that that light doesn't bounce around too much.

There's lots of different ways that you could use this information.

I've been Mr. Wilshire.

Thank you very much for listening.